In a conventional hard disk drive, recording density becomes higher with higher capacity and an interval between adjacent tracks on a disk becomes narrower. Therefore, when data is magnetically written to the track, data of the adjacent track might be magnetically deteriorated. In a recent hard disk drive, data refresh (rewrite) is performed for recovering data deterioration in the adjacent track due to data write operation. For example, the data written to the track adjacent to the track in which the number of times of data writing reaches a prescribed number is read and the read data is rewritten to the same track.
When power shutdown or a voltage drop occurs during the writing to the disk, the hard disk drive finishes the writing after writing to the end of one sector to which the writing is performed at that time. However, when the sector length is long, there is possibility that the writing to one sector cannot be completed due to the voltage shutdown or voltage drop and write data is interrupted in a halfway position of the sector. In the case of the data refresh also, in the hard disk drive, when the power is shut down during operation to rewrite the data read from the track to be refreshed to the same track, the data might be lost. As a measure against this, there is a case in which the read data to be refreshed is stored in a backup area in advance and then rewritten to the track from which this is read.
However, when the backup is performed, the data refresh takes time.